The world’s longest-lived hedgehog on record lived eight times longer than the typical lifespan. This small mammal from Denmark reached at least 16 years, an extraordinary age since hedgehogs usually live about two years on average.
Despite their spines and shy demeanor, hedgehogs (Erinaceus europaeus) have earned widespread affection for their chubby bodies and endearing faces. Yet populations of this species are declining significantly in many places.
In the United Kingdom, a recent study by the British Hedgehog Conservation Society shows urban hedgehog populations have fallen by about 30% and rural groups by up to 50% since the turn of the century. The concern over this decline spurred interest in better understanding the hedgehog’s life and death processes.
To address this concern, the Danish Hedgehog Project emerged as a citizen-science initiative. Volunteers collected deceased hedgehogs for laboratory evaluation, aiming to reveal patterns in age and causes of death across different environments.
Researchers attempted to determine age and death causes by counting growth lines in the hedgehogs’ chins, a method akin to reading tree rings. This approach helps scientists estimate how often the animal hibernates and, consequently, its age.
The jawbones of hedgehogs show growth lines because metabolism slows during hibernation, which can lower calcium levels and slow or pause bone growth. These lines make it possible to count hibernation cycles and infer age.
Biggest threats: traffic and cars
With more than 400 volunteers, researchers collected 697 deceased hedgehogs from across Denmark, roughly evenly split between urban and rural areas. The findings, published in the journal Animals, identify traffic as the primary danger. More than half (56%) of hedgehogs died while crossing roads, with about 22% dying after vehicle-related incidents or being found on roads, and another 22% dying from natural causes.
Although several long-lived individuals aged 16, 13, and 11 were documented, the average lifespan remains about two years. Nearly one-third (30%) of the sampled hedgehogs died before reaching their first birthday.
Pathways to death include crossing roads during July, which overlaps with the mating season. Hedgehogs often travel long distances to find mates, increasing the likelihood of traffic exposure, according to the researchers.
The scientists also collected tissue samples to assess kinship, exploring whether a shared ancestry could influence susceptibility to diseases passed through generations. It was confirmed that hedgehogs show a degree of inbreeding, yet this did not seem to shorten their lifespans. In a population at risk, finding suitable mates is challenging, which can elevate inbreeding concerns.
“This discovery is promising for conservation efforts,” the researchers note, highlighting a potential positive shift in protection strategies for hedgehogs.
Reference report: https://www.mdpi.com/2076-2615/13/4/626
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